Vulnerability assessment after chlorine disinfection in drinking water distribution system.

Disinfection of drinking water is usually achieved by means of chlorine compounds for their effectiveness and low cost. They ensure a residual concentration in the water supply system (WSS), which reduces the risk of pathogenic contamination and limits the proliferation of microbial species. However, chlorine reacts with the organic matter in the water producing disinfection byproducts (DBPs). Some DBPs, such as trihalomethanes (THMs) have carci nogenic effects on human health and then their concentration has to be monitored and maintained below fixed values. In this context, the objective of present paper is to show a procedure for performing a vulnerability analysis respect elevated THMs exposure in WSS. The introduction of specific index parameters allows to identify the more critical nodes of the system respect to different kind of exposure, high concentration exposure for a short period or chronic exposure to low THMs concentrations, which are both important for epidemiological studies. The analysis is applied to the real water distribution system of Cimitile, a town in South Italy, in which water is disinfected through sodium hypochlorite. The results show that the considered parameters identify different vulnerable nodes respect to the different kind of exposure. The presented procedure may be also useful for implementing methodologies for the optimization of the chlorination process in water supply systems.